This invention is directed to a method of designing and/or visualizing at least one roll/felt combination in the wet press of a paper or cardboard making machine. DE 38 35 641 A1 discloses a method of controlling and/or monitoring the drying process of a paper or cardboard web.
In this method, the air distribution system of a so-called yankee cylinder is triply divided, and a computer is used to control the drying process. Controlling and monitoring the drying process of the yankee cylinder is carried out on the basis of an on-line simulation program with the intention of achieving improved paper quality and more effective drying both in respect of energy consumption and of the actual drying process. To this end a process model is utilized which was established on the basis of trial runs, on-line measurements and/or the drying theory. From a so-called type file or recipe file, set-point parameters in accordance with the web types to be run are entered into the process model, and at predetermined time intervals the simulation program is provided with fresh initial values which are supplied by measuring transducers of the drying process. It is stated that thereby the disclosed process model is adaptive. Hence, the known simulation program will calculate, for instance, the evaporative capacity for every segment of the web to be dried, the dry content and temperature of the paper as well as the energy consumption of the individual drying segments on the basis of the initial values. Additionally, it is possible to determine the velocity, humidity and temperature of the blow air.
In contrast with the drying method disclosed in DE 38 35 641 A1 with air flows directed against the web, there are paper making machines including dewatering members which comprise wet press felts, drying screens, and rolls. By means of wet pressing, as it is called, the paper or cardboard web is drained or dewatered in controlled fashion, the respective machine covering governing the quality of the finished products, the smooth running of the press, and the service life of the felts.
In this respect, the performance of the covering within the press is dependent on the defined roll configuration which in its turn interacts with the felt material.
The alternating effects and influencing parameters of roll/felt combinations in wet presses are extremely complex, and undesirable and unforeseeable alterations in quality or undesirable limitations in productivity during operation of the paper making machines will result due to clogging of the felt in operation. Prior known designing methods in respect of configuring an optimum roll/felt combination rely on sometimes extensive test runs and investigations of modifications necessary on site at the customer""s plant, but such investigations are highly time-consuming and costly.
It is therefore the object of the present invention to provide a method of designing and/or visualizing at least one roll/felt combination in the wet press of a paper or cardboard making machine, said method being capable of acquiring the complex processes in the wet press under consideration of the existing multiplicity of influencing parameters and to represent these processes in a simple and clear way, and particularly customer-specific initial approximations in respect of critical problems of felt design should be capable of being found with a view to optimum efforts in time and costs. The method according to the present invention endeavors to achieve decisions concerning application technology within shorter time periods, wherein operations may be predicted, visualized and tested direct on site, for instance when advising the customer or with already existing plants. Additionally, an analysis of problems that may occur should be executable by means of the invention in a fast and cost-efficient way.
The object of the invention is solved with a method as set out in the teachings of claim 1, and the dependent claims comprise at least suitable embodiments and further developments thereof.
The basic idea of the present invention resides in performing a functional analysis of individual roll/felt combinations of presses with reference to a standard database and to predetermined, easily visualizable known press configurations while in the first place not requiring individual considerations in respect of the multiplicity of complex parameters characteristic for the wet pressing and drying process.
To this end, computing steps for showing the result are shifted to the background particularly when there exist altered input parameters, while the execution of the required arithmetic operations occurs nearly simultaneously, so that a feedback of altered parameters in respect of the dewatering capacity and the performance of the wet press may at any time be fetched for analysis, and especially also process-related analysis.
From a set of offered press configurations the present method accordingly selects the respective actual configuration that is to be designed or visualized, wherein additionally the respective application and the desired paper or cardboard quality may be considered as a criterion governing the selection.
Subsequently, within the selected press configuration, a press, i.e. a roll/felt combination, will be selected and relevant initial machine and roll parameters of the selected press will be read and displayed in the internal database.
Due to the reading of database standard parameters a reasonable set of data will be available for starting the designing process while actual technical facts are taken into consideration.
Due to the fact that the database is updated in the sense of a self-learning process, as will be possible in an advantageous embodiment of the present invention, the method will be qualified in the course of its application so that by making use of the existing computer system, the inputting efforts will be further reduced, on the one hand, and the meaningful content of the displayed results will be enhanced, on the other hand.
On account of a multiplicity of spreadsheet-like allocations of standard parameters and results to be displayed upon reference to these standard parameters, the respective arithmetic efforts are reduced. In other words, a recalculation of results has to be executed only upon a change of the input parameters provided there are no previously calculated results for these input parameters present in the database. This measure renders the method according to the invention suitable for on-line process control so that it may accordingly also be used for continuously monitoring and controlling wet presses in paper and cardboard making machines.
After calculation and display of the results relating to the current dewatering performance of the respective selected press it will be possible to make a controlled alteration of machine and/or roll parameters of the selected press.
It is an essential feature of the present invention that the reading of relevant felt parameters to be allocated already starts when reading or re-writing machine and roll parameters from the and into the standard database, respectively. Such reading of felt parameters, or also a calculation of values characteristic for the dewatering performance is always executed in the background. It is possible by means of such background calculations to minimize the amount of image data required for visualization, on the one hand, and to provide in good time the connection between the properties of roll and felt, i.e. the concrete roll/felt combination, which is required for displaying the result, on the other hand.
Due to the felt and roll analysis which is performed in quasi-parallel fashion and the separate displaying of the respective analysis results under consideration of the values required for the interaction between the paired combination, the otherwise hardly recognizable performance of the wet press is more easily represented. In particular, due to the well arranged representation it is more easily possible in respect of the controlling and monitoring tasks to recognize counter-measures more readily when an alarm is being triggered due to limit conditions of the dewatering process having been reached, so that the proper measures for eliminating any hydraulic overload on the system may be introduced as quickly as possible.
Subsequently, the change in machine and/or roll parameters of the selected press required for the design of the roll/felt combination will then, due to the changes in parameters, lead to an altered dewatering performance of the roll/felt combination of the press, such performance being continuously calculated anew and displayed at least in part as a trend display.
Due to the above-mentioned simultaneous existence of the arithmetic results, switching between roll and felt analysis may be done at random, wherein each presentation of results is provided with input areas for renewed altering and setting of machines and rolls or of machine and felt parameters.
In a preferred embodiment of the method according to the present invention, continuous altering and setting of machine, roll, and/or roll/felt parameters is automatically performed with the intention to provide for any press configuration a roll/felt combination and/or a non-woven felt structure that is distinguished by a predetermined maximum dewatering capacity.
In this embodiment of the method a calculating cycle is triggered at the input side, in which the computer system automatically starts to execute the designing procedure right through until limit values or limit loads are reached, and the obtained results are displayed.
The above-described method is repeated for further presses of the respective press configuration, in which system-proposed data for the further presses are read from the standard database. Essential machine parameters as well as stock parameters which govern the quality of the paper or cardboard will be maintained as higher ranking influencing parameters and will be taken over until a new press configuration is selected.
The standard database, which for instance is based on experience or on previously calculated values, includes linked presetting data for all press configurations, but these data may be changed in the analysis or design process in respect of the roll/felt combination. It is within the scope of the invention that values obtained by calculation on the basis of new machine, stock, roll and/or felt parameters and characteristic of the respective pairing may be stored as new standard data and may be included within the standard database. Establishing new standard data may be realized by an updating operation by the execution of self-learning steps.
To enhance the visualization of the obtained results or the displayed parameters, these may be displayed on the monitor of the computer system in different graphic and/or colored form. In a specific embodiment, the dewatering performance of the respective press is represented by a display of the product-related results in a first corresponding form, of the water-related results in a second corresponding form, and of the variable input parameters in a third corresponding form.
With the method according to the present invention it is possible by means of a few simple inputting operations and by reference to a computer system to represent complex procedures in the wet press of a paper or cardboard making machine, wherein a great number of influencing parameters may be recorded which are, however, presented in simple form so that even under consideration of the important interactions between individual parameters the distinctiveness of the display will be retained.
Due to the parallel running of roll and felt analysis which is, however, always kept in the background, random switching between displays is possible while the original input values of the respective press are retained. A controlled change of the stock or machine parameters may be executed both from the roll analysis and from the felt analysis, i.e. after calling the respective submenu.
When selecting a further press of a press configuration, the system starts with a system proposal in respect of the new roll/felt combination, while essential machine and stock parameters are taken over. These parameters, especially the machine speed, the paper quality, the stock temperature and other stock parameters, will be retained for all presses of the configuration until a modification of these higher-ranking influencing parameters is effected.
By the present method it is possible in a very simple way to find out what effects an increase in pulp temperature, a change in line-load, a change in machine speed, stock feed or degree of beating will have on the ultimate dry content of the paper or cardboard. Likewise, immediate visualization of the effects of an increase in speed, for instance as related to the loss of dry content, will be possible.
Another advantage of the method resides in the process-related simulation of the performance of the roll/felt combination, especially the long-term performance of the felt under consideration of clogging of the felt surface, so that the time period of maximum felt capacity and the timing for maintenance work may be determined already prior to a resulting deterioration in quality such as, for instance, crushed paper. Finally, it is possible to choose from among the set of calculated results a subset for displaying limit conditions during the dewatering process. These limit conditions are, in particular, a maximum pressure of the press resulting from the properties of roll linings which are for instance elastomeric, a negative water balance, or an excessively high resistance to flow within the felt possibly leading to hydraulic overloading and resultant vibrations, a short useful life of the felt and felt breakage.
The present invention will be explained in detail by way of an embodiment thereof and with reference to the drawings.